Research On Simultaneous Transmitting And Transmitting Technology Of Radar Jammer System

As an important electronic warfare equipment,radar jammer usually has the functions of reconnaissance receiving and jamming transmission.Radar jammer can identify and jam enemy radar.In special application scenarios such as missile-borne and airborne,due to the limitation of the distance of the transmit-receiver antenna,the transmit-receiver isolation of the radar jammer is low,and the self-interference signal will enter the receiving antenna,resulting in a serious decline in the performance of the jammer or even failure to work normally.Therefore,how to improve the transmit-receiver isolation is a key issue for missile-borne radar jammers.At present,in practical applications,the transmit-receiver time-sharing strategy is generally used to improve the transmit-receiver isolation of radar jammers,but it reduces the reconnaissance receiving sensitivity,parameter measurement accuracy,interception probability,and minimum interference range of the jammer.Aiming at the above problems,this thesis will study the radar jammer based on the simultaneous transmitting and receiving system,focus on analyzing the advantages of the simultaneous sending and receiving strategy and the existing self-interference problems,and give a self-interference cancellation scheme.The main work of this thesis is as follows:Firstly,for the missile-borne radar jammer,analyze its reconnaissance receiving and jamming performance under the strategy of time-sharing and simultaneous transmission and reception.Based on the transmit-receiver time-sharing strategy,the calculation expressions of the performance evaluation indicatrix of jammers such as receiving sensitivity,parameter measurement accuracy,interception probability,and minimum jamming distance are derived,and the relationship between the performance indicatrix and the intermittent sampling period,the receiving duty cycle and the transmitting duty cycle is given.Then,under the premise of the infinite transmit-receiver isolation,the advantage of radar jammer using simultaneous transmit-receiver strategy compared to transmit-receiver time-sharing is analyzed from a theoretical point of view.Next,for the self-interference problem of simultaneous transmit-receiver radar jammers,when the transmit-receiver isolation is insufficient,in this thesis,from the perspective of the self-interference transmission channel and the nonlinear characteristics of the device,the Rice channel and the Hammerstein model are used to mathematically model the formation mechanism of the self-interference signal,and the influence of the self-interference on the performance of the jammer is analyzed.Finally,the advantages and disadvantages of radar jammers under different transmit-receiver strategies are verified by simulation experiments.Secondly,in view of the problem that the self-interference of simultaneous transmitreceiver radar jammers leads to the degradation of reconnaissance receiving and jamming performance,a self-interference cancellation scheme based on radio frequency(RF)cancellation and broadband nonlinear digital cancellation is proposed.The multi-tap selfinterference cancellation technology is used to suppress the self-interference of the RF front-end,prevent the saturation of the low-noise amplifier and ensure that the ADC can quantify the received signal normally and effectively.Then,based on the formation mechanism of the self-interference signal and the idea of "width narrows",a broadband nonlinear digital self-interference cancellation method is proposed to eliminate the linear and nonlinear components of the residual self-interference signal,and further improve the transmit-receiver isolation.Finally,the theoretical analysis and simulation results show that the self-interference cancellation scheme proposed in this thesis can fully eliminates the broadband linear and nonlinear self-interference components,and greatly improves the performance of the simultaneous transmit-receiver radar jammer.